One of the current standard recommendations on method for coding/decoding digital images with an interlaced structure is ITU-TH.262NN which is capable of efficiently coding/decoding TV signals such as NTSC.
There is another method for coding/decoding digital images including not only pixel luminance and chrominance signal values, but also form information signals that indicate the form of an object, which is adopted as an evaluation model of the ISO/IEC MPEG4 (ISO/IEC ITC/SC29/WG11 N1469 November 1996).
This method is characterized by the ability not only to effectively reduce the amount of codes by coding/decoding luminance signal and chrominance signal for only significant pixels indicated by the form information, but also to easily synthesize images in accordance with the form information.
However, the MPEG4 evaluation model described above does not take into account images which have an interlaced structure in which one frame contains 2 fields, which prevents efficient coding/decoding of input images with the interlaced structure.
In addition, the H.262 takes account of a motion compensation method and discrete cosine transformation a by taking the interlaced structure for luminance and chrominance signals into consideration, whereas it uses as the method for coding binary images which indicates a significant form, special methods such as down-sampling, up-sampling, and prediction of variation locations of pixel values that are not considered by the H.262, which prevents the coding/decoding means applicable to the interlaced structure used in the H.262 from being simply adopted.